如果你逐个删除，那么下面给你删除行的索引

If you remove by-one, then the following give you index of deleted row

func delete(at offsets: IndexSet) {     
      self.symptoms.remove(atOffsets: offsets)

      // here I want to make the HTTP request
      let index = offsets[offsets.startIndex]

      // ... use index in HTTP request
}